EP-B1-1 176 950 relates to a method and a disposable device for providing a coating on a tablet, capsule, pill or the like, in order to improve the taste and the swallowing characteristics of the tablet. The coating is applied manually with the device and it replaces the taste of a given tablet with a more palatable taste. EP-B1-1 176 950 is incorporated in a whole as a reference.
Many types of substances can be used with this coating technique in order to apply a coating to a tablet. The present inventors have however discovered that in order to be able to coat different types of tablets, in size and shape, with the same device (which is advantageous since it is less economical and practical to produce different devices adjusted for different sizes and shapes of tablets) and still obtain an enclosing coating that is thin and even you need to have a coating composition presenting specific viscoelastic rheological properties at room temperature. The reason why it is beneficial with a fully enclosing coating is that it better can camouflage a tablet's possible bitter taste and also better improve the swallowability of tablets with a rough surface. The reason why it is beneficial with a thin and even thickness of the coating is that if the coating is uneven the coating could get too thick on some areas making the tablet's size bigger and therefore harder to swallow. If the coating is too thin on some parts the coating could dissolve too quickly in the mouth, revealing the sometimes bad taste and rough surface of a tablet. A coating composition with a suitable viscoelastic rheology can be reshaped and stretched to a great extent forming a thin and even film and is therefore suitable to be used with this coating technique.
The patent EP-B1-1176950 gives little advice in how to formulate a suitable coating composition. The only examples of ingredients suggested to be used in EP-B1-1176950 to formulate the coating composition are gelatine and glucose and no directions are given concerning the amount of the ingredients to be used. When using only gelatine and glucose the present inventors have not succeeded in formulating a stable viscoelastic coating composition that is suitable for coating of different types of tablets, in size and shape with the same device.
The formula with best rheological properties using only gelatine, glucose and water was obtained by dissolving gelatine (type A, 260 bloom, SG-722 from Gelita Sweden) and glucose separately in water and then mix it and boil it and ascertain that the final compound consists of 1.3 weight-% gelatine, 1.0 weight-% water and 97.7 weight-% glucose. However, this composition is not stable and will crystallize within two weeks resulting in that the viscoelastic properties are lost and the composition becomes a non-homogenous mass with hard sugar crystals, not suitable for the coating technique. This formula would therefore at its best result in a product with a shelf life of less than two weeks, which naturally is very disadvantageous for a consumer product.
Further on a coating composition consisting of gelatine, glucose and water gives a coating that is relatively sticky to fingers and teeth. The stickiness to fingers is negative since it makes the coating less pleasant when the coated tablet is held in the hand before swallowing. The stickiness may also increase the amount of dirt and bacteria etc. that clings to the tablet before swallowing. The stickiness to teeth is negative since the coated tablet may therefore cling to the teeth when the tablet is put into the mouth, which is unpleasant and it can also make the swallowing of the coated tablet more difficult. It is therefore desirable to have a coating compound with a relatively low stickiness.
Play putties based on cross linked polymer solution often have a suitable stable visco elastic rheology. Further these play putties are generally non sticky to fingers and teeth. However, these types of masses are not suitable to be used as coating compositions mainly since these compounds contain borax, which is not permitted as a food additive in many countries and since they have a low solubility in water which can delay the absorption of an ingested drug in the stomach. The present inventors have albeit much effort not succeeded in finding a previous developed suitable viscoelastic mass based on food approved ingredients.
Tests were also performed on many different confectionary masses but it was found that none of these had suitable viscoelastic properties. Generally they were either mostly elastic (e.g. jelly confectionary) or mostly viscous (e.g. soft caramel).
Apart from the above mentioned desirable properties of the coating compound the inventors have found that it would also be preferable if the coating composition could be sugar free, contain saliva stimulating ingredients, be slippery in the mouth in order to make the tablet easier to swallow, be allergen free, has a low water activity preventing bacterial growth, be easy to deposit into the device during manufacturing, dissolve quickly from the tablet in the stomach and contain only ingredients not known to interact with medical substances.
It is an object of the present invention to solve the above mentioned obstacles and present a suitable coating composition to be used with the coating method and device described in EP-B1-1176950.